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First author: Michael J Prigge; Affiliations: University of California, San Diego (加州大学圣地亚哥分校): La Jolla, USA
Corresponding author: Mark Estelle
The TIR1/AFB auxin co-receptors mediate diverse responses to the plant hormone auxin. The Arabidopsis genome encodes six TIR1/AFB proteins representing three of the four clades that were established prior to angiosperm radiation. To determine the role of these proteins in plant development we performed an extensive genetic analysis involving the generation and characterization of all possible multiply-mutant lines. We find that loss of all six TIR1/AFB proteins results in early embryo defects and eventually seed abortion, and yet a single wild-type allele of TIR1 or AFB2 is sufficient to support growth throughout development. Our analysis reveals extensive functional overlap between even the most distantly related TIR1/AFB genes except for AFB1. Surprisingly, AFB1 has a specialized function in rapid auxin-dependent inhibition of root growth and early phase of root gravitropism. This activity may be related to a difference in subcellular localization compared to the other members of the family.
TIR1/AFB生长素共受体介导植物对于生长素的多种响应。拟南芥基因组编码六个TIR1/AFB蛋白,分属在被子植物辐射之前就已经形成的四大类中的三类。为了研究这些TIR1/AFB蛋白在植物发育过程中的作用,作者构建了所有可能的多突变株系,通过大规模的遗传学分析对这些蛋白进行功能鉴定。作者发现6个TIR1/AFB蛋白同时功能丢失会导致胚胎早期的发育缺陷,最终引起种子败育,然而单个TIR1或者AFB2野生型等位基因回补六突植株足以保证其完成生活史。作者的分析显示除了AFB1基因之前,其它所有的TIR1/AFB蛋白即使是亲缘关系最远的两个蛋白之间,也都存在功能重叠。令人惊讶的是,AFB1基因具有快速生长素抑制根生长以及作用于根向重力性早期阶段的特异功能。这种特殊的活性可能跟AFB1基因与其它成员之间亚细胞定位的差异有关。
Background
Auxin,生长素是一类植物激素,其几乎影响着植物生长和发育的方方面面。生长素合成、信号转导以及转运相关基因的突变均能够引起植物体内生长素稳态的不平衡,从而导致各种各样的异常表型(如下图;doi: 10.1186/s12915-016-0291-0)。
生长素对于基因的转录调控主要涉及三个家族的蛋白:转录因子ARFs、转录抑制因子Aux/IAAs以及TIR1/AFBs。在没有生长素时,Aux/IAAs会结合到ARFs上,抑制ARFs作用于基因的转录调控;而在有生长素时,TIR1/AFBs与Aux/IAAs形成共受体复合物,其后Aux/IAAs蛋白会被降解,从而释放了ARFs,其开始作用于下游基因的转录调控(如下图;doi: 10.1186/s12915-016-0291-0)。
TIR1/AFBs除了在上述途径中发挥功能外,最近的一些研究显示TIR1/AFBs可能还作用于根以及发育中的根毛中的快速生长素响应,且该作用独立于基因的转录调控(NC, 2018: 10.1038/s41467-018-03582-5;NP, 2018: 10.1038/s41477-018-0190-1)。
通讯:Mark Estelle (https://biology.ucsd.edu/research/faculty/mestelle)
研究方向:利用模式植物拟南芥研究植物中的生长素响应通路。
doi: 10.7554/eLife.54740
Journal: eLife
Published online: February 18, 2020
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